2026-11-10 Steinheil Munchen Auto-Quinaron 35 mm f/2.8

    This Steinheil Munchen Auto-Quinaron 35 mm f/2.8  (1958) had a stop-down mechanism that was not working, so I was given the chance to see if I could fix it. Rotating the f/stop ring didn’t do anything, the lens stay wide open all the time.
    Maybe I should introduce the lens by the camera it was made to fit. The German Exakta SLR’s had a shutter button on the front of the camera near the lens mount. Clever lenses like this one had a projecting “arm” that ended up in front of the shutter button on the camera. Many lens designers made a stop down arm that got depressed as you pressed in until it pressed against the camera’s shutter button and the shutter fired. The view would get dimmer as the lens stopped down but how quickly that happened was up to how fast you pressed in on the shutter release/stop-down lever.
    Steinheil developed a different technique. On this lens the outside satin finish chrome ribbed lever would be rotated down. This makes the stop down action rotary while a metal shutter release shaft is extending at right angles to press the shutter release on the camera body. 
    Above the ribbed lever there is a cable release socket.
    Closer to the lens on the black extension “arm” there is a two position (push/pull) satin finish knob that changes the aperture action from auto stop-down to manual stop-down. In the auto position the lens is wide open until the shutter lever is depressed. In the manual position the aperture is what is set on the aperture ring.

    The lens has from front—

• focus ring (knurled aluminum)
• (an inset) green anodized ASA ring (further around has aperture numbers)
• red guide numbers (further around has markings that align with distance scale)
• distance scale in feet
• lens focus point  (in red, bracketed by depth-of-field scales)
• aperture ring

    It seems the green ring can be used to set the guide number of the flash to the ASA of the film and then the lens will show you what aperture to use at different distances. It is a clever system that makes using guide numbers redundant.
    For now note the small screw in the black ring. There are three small screws in the black “C” ring (the ring is not a complete circle) that cover about five larger screws that hold the lens mount on the rear of the lens. Unlike most Japanese lens mount designs, the Exakta mount has no screws attaching the mount to the lens coming from the camera’s direction. Instead the screws come in from the sides.
    

That aluminum button pops in and out. Pressed in—towards the label—the lens is automatic. Pulled out the lens becomes non-automatic (we would say manual).

    This shows the third of the three screws in the black ring. Note how tight all the clearances are—

• between the aperture knurling and the satin chrome button
• between the black shut-down mechanism box and the satin chrome lens       barrel
• between the stop-down lever and the stop-down mechanism box

    

    Initially it seemed easiest to remove the four small screws in that satin chrome plate off to the left. The thinking was taking the cover off the stop-down mechanism might show a way forward. It is a false path, although it does make it easier later when you attempt to clean the clockwork action of the stop-down gearing. You can save taking these screws out until you have the whole lens mount off the lens.
    This is going to be a bit frustrating to anyone hoping for step-by-step repair images. I gave up trying to fix this lens. I will try to explain why simply. Once I had the lens apart I found the black stop-down “box” contains a clockwork series of gears that baffles me. It consists of a small transmission held in place by two screws that can be primed when rotated one way and then when it unwinds, returns the stored spring power. That would have been fine except the priming and unwinding is transferred to a small toothed “wedge” that in turn runs a second series of gears. It seems strange to have the 40º of rotation of the aperture ring transfer to a really tiny toothed wedge. It probably is also 40º of a wedge, but really tiny.
    Why all this gearing you ask? 
    

     Inside the lens has an aperture mechanism that mimics the exterior aperture ring. It has ridges that mate with the gear-box. Apparently that (dratted) small gear wedge pulls the iris blades to their setting. And here is the catch that defeated me. You have to preset either the inside position of the iris blade ring or the outside aperture setting, or perhaps preload the gear box and/or know what setting the auto/non-auto button is in while trying to slide the entire rear mount on the protruding lens bits. Needless to say, there was a time there I wasn’t sure I could ever get the lens to fit together again. 
    I must also admit that two of the five screws simply wouldn’t thread back into the lens mount. I thought I had—like all good repair people—placed the parts in order of their removal. Then I thought I had also started at the same point putting the screws back. 
    Remember the two screws holding the gear train in place? Seems I had placed one of the screws I needed later in one of its two holes. Once I succeeded in loosely getting screws started down the counter set holes I finally got everything reassembled.    

    For one brief second the lens showed it was slightly stopped down. Then I touched either the auto/non-auto button or the trigger arm and the lens popped open and stayed that way. The exterior aperture ring isn’t moving anything. 
    If I was a good camera repair person I would simply shrug and dive back in. Knowing what I do now, I would take better note of which screw goes where, but that is a an almost insulting note to make to oneself. I still have no idea how those little bitty gears manage to mesh while you have to jam the lens together. 

Notes—

1. I did wash off the gear box and stop-down mechanism with lighter fluid. The result was a much looser action to everything. There are places I would suspect some really high class grease should be. 
   
2. I did use some sewing machine oil on the spring storage gear shafts that were exposed, but the other ends of the shafts were attached by screws to the lens mount.

This leads me to a final point. I would feel better if the owner would sell me the lens. If it was my lens I would keep trying until I had to give up. But that moment I wasn’t sure I could reassemble the lens was terrifying. What if I had to return a fine looking lens to the owner in pieces, or with stripped or destroyed parts? Imagine how that would make you feel.